Machine for generating paraboloids of revolution



May V29,- 1941. J. F. sToNE ETAL MACHINE FOR GENERATING PARABOLOIDS 0FREVOLUTION 4 Sheets-Sheet 1 Filed Jan. 5, 1940 QA d wr k2 Hl l. Il IMEREE funn WT'WIIIIUl I O MWNN WN @MN MN. w w WN NN W r um o mv Nw? MW 1Nl QN/mv/Jr QW MN ARN' m NN o m mm s N W g S, w @a .N NN

May 20, 1941. J. F. STONE ETA. 2,242,664`

MACHINE FOR GENERATING PARABOLOIDS OF REVOLUTION Filed Jan. 5, 1940 4sneetssneet 2 g vwe/wtom/ Ju Per/yU/ey May 20 1941 J. F. STONE' Erm.2,242,664

MACHINE FOR GENERATING PRBOLOIDSl OF REVOLUTION Filed Jan. 3, 1940 4Sheets-Sheet 5 ya www@ .May 20, 1941. J. F. STNE 'HAL 2,242,664

MACHINE Foa GENERATING PARABoLoIDs oF REVOLUTION Filed Jan. 5, 1940 4sheets-smul! F .4. I Jay/7% ll I /J L l f Patented May 20, 1941 UNITEDSTATES ATENT OFFICE MACHINE FOR GENERATING PARABOLOIDS OF IREVOLUTIONThis invention relates to a machine designed to generate and produceparaboloids of revolution. In its particular aspects, it may be used forgrinding or polishing parabolic mirrors, or for machining or grindingdies, forms or molds for pressing, casting or forming parabolic shapes.

It is an object of the invention to provide a practical and efficientmachine for the purposes set forth and one which may be adjusted quicklyfor parabolas of revolution of any diameter Within its capacity, and ofany focal length desired, and which will generate forms either concaveor convex.

For a further understanding of the invention, reference is to be had tothe following description and the accompanying drawings, in which:

Fig. 1 is a side elevational view of a machine constructed in accordancewith the present invention for producing paraboloids of revolution, theadjusting elements of the machine being shown in positions which theyoccupy at the commencement of an operation;

Fig. 2 is a similar View disclosing the' parts of the machine at thepositions which they occupy at substantially the completion of a givenoperation;

Fig. 3 is a vertical transverse sectional View taken through the machineon the plane indicated by the line III-III of Fig. 1;

Fig. 4 is a similar view on the plane indicated by the line IV-IV ofFig. 1;

Fig. 5 is an enlarged vertical and longitudinal sectional view on theplane disclosed by the line V-V of Fig. 4, the movement regulatingmembers shown in this ligure occupying the same relative positions as inFig. 1;

Fig. 6 is a similar view showing the positions of the movementregulating members intermediately positioned between those disclosed inFigs. 1 and 2;

Fig. 7 is a diagrammatic view setting forth the development of aparabolic curve;

Fig. 8 is a similar view of another curve;

Fig. 9 is a detail side elevational view illustrating the movementregulating members of a machine in positions to produce convexcurvatures; y

Fig. 10 is a detail perspective View of one of the slide members.

The principle upon which our improved machine operates is based on thewell known method of developing a parabolic curve, as shown in Figs. 7and 8, but for generating a paraboloid of revolution,it is necessary toconsider only onehalf of the curve, i. e., that located on either sideof the axis AB.

To facilitate a clear understanding of the invention, the line FD inFigs. 7 and 8 will be called the sine, the lines Aa', Ab', Ac', etc. aredesignated hypotenuses. Further, the points a', Zi', c', etc. formed bythe intersection of the hypotenuse lines with the sine line are termedabscissae, and the distances Ba., Bbl, Bc, etc. are ordinates, Where theparallel lines defining these distances intersect the parabolas curveCAD.

It will be seen, by comparing Figs. 7 and 8, that the focal length ofthe parabola may be altered by changing the ratio of the abscissaespacing in relation to the heights of the ordinates. In Fig. 7, Xindicates the focus, while in Fig. 8, the abscissae spacing beingone-half that disclosed in Fig. 7, the focal length is doubled, thefocus being located at X'.

Our improved machine is designed to reproduce automatically theprocesses followed in developing parabolic curves as indicated in Figs.7 and 8, except that, in effect, the machine uses an infinite number ofsines, hypotenuses, abscissae and ordinates.

Y Figs. 1 and 2 show the various elements of the machine and theirpositions and relations when grinding a parabolic mirror. Fig. 1illustrates the grinding wheel at the center or axis of the mirror', andFig. 2, the positions of the parts of the machine after the wheel hastraversed the face of the mirror and arrived at the edge.

In the drawings, the numeral I represents a mirror to be ground to aparabolic contour, the element 2 being a face plate upon which themirror is mounted, and clamps are indicated at 3 for centering andsecuring the mirror in its position on the face plate. The face plate 2is carried on a vertical shaft II, running in'a bearing in the bracketIi, forming a part of the base plate 1. A pulley 5 is keyed to the shaft4 and is suitably actuated so that the mirror I may be rotated. Anabrasive wheel 8 is mounted to rotate on a spindle 9 by means of apulley Il). The spindle 9 is attached to a vertical slide II, the latterhaving means by which vertical adjustment of the wheel 8 may be made as,for instance, by a screw operated by the ball crank I2. The slide II maybe dovetailed to the end of a reciprocating frame I 3, which frameserves to traverse the grinding Wheel across the face of the mirror fromthe center of the latter to its edge.

The frame I3 is provided with eight pivots., two of which are indicatedat I4, and on. which are mounted bearing shoes I5, these being free torock on pivots I4.

The bearing shoes carry the weight of frame I3, and they lslide uponpivoted planes which, for convenience and description, will be calledhypotenuse bars and are indicated at I1. These bars are pivoted as at I8in connection with the upper ends of brackets I9. When the position ofthe grinding wheel 8 is directly over the axis of the mirror beingground, it is essential that the pivots I4 and I8 be axial with eachother. The free end of each hypotenuse bar is supported on its bottomsurface by a bearing shoe 20, pivoted at 2I in the upper ends of bars 22which slide in guides 23. These bars may be called sine bars, since theyare in effect equivalent to the line FD in Figs. 7 and 8. These barsmust be parallel to the axis of the mirror supporting shaft 4.

Mounted on pivots IS at the lower ends of the bars 22 are shoes 24 whichbear upon the planes 25 and which may be turned upon pivots 2B car riedin brackets which are a part of the bar shown at 28, the latter beingmounted to reciprocate on the base plate 1. rIhe angle of the planes 25,which may be called abscissae planes, may be adjusted by means of thecalibrated screws 21. The frame i3 and bar 28 are caused to move likedistances and in opposite directions through the medium of the lever 29,pivoted in its center as at 30 to an arm 3I.

The top and lower ends of the lever 29 are pivotally connected withsliding blocks 32, worklng in guides 3d formed in one end of the bar 28and the frame i3. The frame I3 may be reciprocated in any suitable way.In this instance, the base plate 1 is extended to effect the support ofa bracket 63 in which is journaled a shaft E4. The shaft carries apulley 65 driven by a belt or other suitable means. Fixed to rotate withthe shaft 64 is a disk @E having a radially adjustable crank pin 61.Connected with this crank pin is one end of a link 88, the opposite endof said link being pivotally connected as at 69 with one end of theframe I3. This construction, among others which may be used, providesfor the lcontrolled reciprocation of the frame I3 and variations in thelength of its stroke. The bracket 83 is also mounted for slidableadjustment on the base plate 1 toward and away from theiframe by meansof the screw shaft 18 to center the grinding Wheel relative to the axisof the mirror I.

Having described the essential elements of the machine, its operationmay be briey explained.

If the abscissae bars or planes 25 are so adjusted that they areparallel to the hypotenuse bars I1, the abrasive wheel 8, when inoperation, will traverse a straight line and grind a plane surface onthe mirror I.

When, however, the planes 25 are set at any angle to the horizontal,whether mostminute or great, a parabolic curve will be described by thecenter of the grinding wheel during its traverse from the center of themirror to the edge, and the 4characteristics of the curve will dependsolely upon the angle at which the planes 25 are set. A change in theangle of these planes acts to alter the ratios of the abscissae of thecurve to its ordinates or, in other words, the angle of the planes 25determines the focal length of the mirror to be ground, and isequivalent to changing the length of the line FD shown in Figs. '1 and8.

By the use of the graduations on the screws 21,

the machine can at once be set to grind a paraboloid of anypredetermined focal length.

By reversing the angle of these planes, as shown in Fig. 9, the abrasivewheel will grind a convex paraboloid of revolution, this feature beingconvement in punch and die work. It will be seen that the machineautomatically performs the operations followed when drafting the curvesof Figs. 7 and 8.

In operation, the sine bars 22 may be considered to act as an ininitenumber o-f points 1ocated along the sine FD of Figs. 7 and 8. Thehypotenuse bars I1 may likewise be taken as an infinite number ofhypotenuses swinging between F and D, the travel of the grinding wheelbetween the center and edge of the work develops an infinite number ofordinates.

The bars 25 serve as a means to manually change the value of theabscissae from Zero to the maximum value permitted by the particularmachine being used, and also tol change from concave to convex contours.

Obviously a cutter may be used toremove material instead of a .grindingwheel, nor need the periph-ery of the wheel have the shape shown inFigs. l and 2. It must, however, have a line contact on the piece beingworked when the final contour is being generated.

It will be noted in Fig. 3 the arrangement of the shoes I5, riding onthe guides I1, prevents any lateral movements between these parts sothat the frame I3 can have only linear motion in the horizontal plane.Further, in Fig. 3, it will be noted that the center line, indicated atL-L,

` of the axes of the pivot-s is in line with the three planes of thesystem, this line corresponding to the numerals I1 as shown in Figs. land 2.

It is obvious that the machine need not of necessity follow the specificdesign here shown and described, as this arrangement was selected merelyto provide a simple presentation of the fundamental mechanicalprinciples involved in the present invention.

What is claimed is:

1. A machine to produce paraboloids of revolution, comprising a rotarywork-carrying member, a reciprocating frame, a material removing elementcarried by said frame, means for reciprocating said frame transverselyof the work, a guide swingable about a xed pivot, means on said frameslidably engaging said guide and cam means for causing said guide -toswing about its pivot as said frame reciprocates to guide said frame ina feeding movement` at substantially right angles to the axis of saidelement whereby said element is caused to vdescribe a parabolic curve.

2. A machine to produce paraboloids of revolution comprising a rotarywork-carrying member, a reciprocable tool frame, a material removingtool carried by said frame, a guide-way swingable about a iixed pivot inthe plane of movement of said tool frame, means slidably supporting saidtool frame in said guide-Way, means for longitudinally reciprocatingsaid tool frame, and cam means for simultaneously swinging saidguide-way about its pivot to guide said frame in a feeding movement atsubstantially right angles to the axis of said tool whereby the latteris caused to describe a parabolic curve.

3. A machine to produce paraboloids of revolution, comprising a rotarywork-carrying member, a longitudinally reciprocable tool frame, amaterial removing tool carried by said frame, a guide-way swingableabout a fixed pivot in the plane of movement of said frame, meansslidably supporting said frame in said guide-way, a longitudinallymovable, inclined bar, means slidably engaging said bar for swingingsaid guide-Way on its pivot, means for longitudinally reciprocating saidframe and means for simultaneously and oppositely reciprocating saidinclined bar to cause a feeding movement of said frame in a direction atright angles to the axis of said tool whereby the latter is caused todescribe a parabolic curve.

4. A machine to produce paraboloids of revolution comprising a rotarywork-carrying member, a longitudinally reciprocable 4tool frame, amaterial removing tool carried by said frame, a pair of longitudinallyspaced guide-ways swingable about fixed pivots, means slidablysupporting said frame in said guide-ways, means for reciprocating saidframe, cam means for swinging said guide-ways on their pivots, and meansfor so timing the swinging of said guide-ways with the reciprocation ofsaid frame, as to cause said frame and tool to simultaneously partake ofa distributing movement transversely of said work and a feeding movementin a direction at right angles to the axis of said tool. Y

5. A machine to produce paraboloids of revolution comprising arotarywork-carrying member, a reciprocable tool frame, a materialremoving tool carried by said frame, a pair of longitudinally spacedguide-ways swingable about iiXed pivots, means slidably supporting saidframe in said guide-ways, an inclined plane adjacent each guide-way anda vertically reciprocable bar interposed between each guide-way and itsrespective inclined plane, means slidably supporting said bars onrespective planes, means for reciprocating said frame in a distributingmovement from the periphery to the center of the work, and means forsimultaneously reciprocating said inclined planes to cause saidguideways to swing about their pivots whereby said frame partakes ofsaid movement toward and away from said material.

6. A machine to produce paraboloids of revolution comprising ya rotarywork-carrying member, a reciprocable tool frame, a material removingtool carried by said frame, a pair of longitudinally spaced guide-waysswingable about fixed pivots, means slidably supporting said frame insaid guideways, an inclined plane adjacent each guide-way and avertically reciprocable bar interposed between each guide-way and itsrespective inclined plane, means slidably supporting said bars onrespective planes, means for reciprocating said frame in a distributingmovement from the periphery to the center of the work, means forsimultaneously reciprocating said inclined planes to cause saidguide-Ways to swing about their pivots whereby said frame partakes ofsaid movement toward and away from said material, and means for varyingthe angle of inclination of said planes to regulate the parabolic curvedescribed by said tool.

7. A machine to produce paraboloids of revolution comprising a rotarywork-carrying member, a horizontally reciprocating frame, a materialremoving tool carried by said frame, a guideway swingab-le about a ixedtransverse pivot, means on said frame slidably engaging said guide-way,a vertically reciprocating bar operatively engaging said guide-way,means for longitudinally reciprocating said frame, and means forsimultaneously reciprocating said vertical bar to swing said guide-wayon its pivot, the reciprocations of said frame and bar being so timed asto cause the frame and tool to describe a parabolic curve.

8. A machine to produce parabcloids of revolution comprising a rotarywork-carrying member, a reciprocable frame, a material removing toolcarried by said frame, means for longitudinally reciprocating saidframe, a guide-Way swingable about a fixed transverse pivot, means onsaid frame slidably engaging said guide-way, a supporting baroperatively engaging said guideway and reciprocable in a plane at rightangles -to the movement of said frame, a longitudinally reciprocablesupporting member, an inclined plane carried by said supporting member,means on said Vertical bar slidably engaging said plane, and means forreciprocating said supporting member simultaneously with, but in adirection opposite to that of said frame whereby said tool undergoes adistributing movement across the Work while advancing in a feedingmovement toward said work.

JULIUS F. STONE. PERRY OKEY.

